In recent years, there has been a development of an electric key system which does not have a key cylinder at an opening and closing portion of a vehicle or a house. The electric key system functions that when a person with an electric key approaches to the opening and closing portion, the system becomes a reception standby mode, and when it receives an ID code from the electric key, the system unlocks as soon as the person touches a door handle etc.
In this type of the electric key system, it is desired to install an antenna within the opening and closing portion or control portion for opening and closing (inside of a door or a door handle If the opening and closing portion corresponds to the door). Generally, since there Is not much space to install in such places, a bar antenna whose core is made of a material with high permeability is applied.
A known device is disclosed in Japanese Patent Laid-Open Publication No. 5-267922. In the known device, an antenna for a vehicle whose core is made of a laminate of amorphous magnetic alloy ribbons is applied to improve high frequency characteristic and to achieve downsizing.
Another known device is disclosed in Japanese Patent Laid-Open Publication No. 7-221533. In this known device, an antenna applying a laminate of nanocrystalline magnetic alloy ribbons for a material of the core is disclosed, and the antenna is achieved in obtaining a sufficient level of signals, feasibility to downsize, and a stability against a temperature characteristic or time deterioration.
However, in the opening and closing portion, a bending load is applied to the antenna upon opening and closing the door due to vibration. In addition, Impact upon opening and closing the door is large. Therefore, the known devices could be damaged due to these loads. Particularly, in a case of a vehicle door (an opening and closing portion), it receives Impact from both front and back directions of the vehicle upon acceleration and deceleration. Moreover, larger impact (approximately 100 G: G corresponds to a gravitational acceleration) is applied upon closing the door. Thus, an improvement of impact resistance has been a key issue for the antenna for the vehicle door.